Many mechanical assemblies are comprised of a plurality of components that are coupled together to form a unit. Thus, there are a great many applications for fastening elements such as nuts and bolts that are used to couple components together. It can also be appreciated that the security of the component coupling is often vital to the effective operation of the mechanical assembly. Accordingly, the fastener elements are required to be secured very tightly to hold the components in place.
Drive sockets are widely used to manipulate fastener elements such as nuts and bolts. One common socket design includes a cylindrical body with a receiving cavity whose inner surface is formed to engage the planar faces of the fastener element. For example, most nuts and bolts have a hexagonal configuration. Accordingly, the socket cavity is hexagonally broached to receive with exact registry the hexagonally shaped element. The drive socket thus makes driving contact with the planar faces or flats of the fastener element. This design is generally sufficient to apply torque turning loads to fastener elements for rotary displacement in most operative environments.
U.S. Pat. Nos. 3,675,516 and 3,495,485, both to Knudsen et al., disclose drive sockets with splined cavities to accommodate polygonally shaped fastener elements. The particular cavity surface design allows confronting surface engagement with the flats of the element adjacent the corners. When applying torque loads to the element, there is substantially no stripping of the corners of the fastener element.
While generally effective for their operative purpose, these socket drives are not without their shortcomings. More specifically, they do not efficiently accommodate fastener elements of all configurations. In particular, rounded fastener elements do not have flats for cooperative engagement with the operative faces of socket splines.
In addition, frequently a nut forms so tight a union to a bolt or threaded lug that the torque requirement for rotary displacement cannot be effectively applied by these drive sockets. A classic example of this situation involves the lug nuts on the wheel of an automobile. In attempting to break a lug nut "free" from its adhesive-like union, the splines of the socket cavity often slip along the flats of the lug nut and across the corners. This eventually leads to the rounding of the corners, also known as the stripping of the lug nut. Once a lug nut is stripped, a standard drive socket cannot be used to accomplish removal. In fact, it is possible for a lug nut to become so damaged that it may only be removed by cutting the threaded wheel lug on which it is fastened. This is both costly and inconvenient. Typically, a professional mechanic must be employed to replace the lug after cutting.
U.S. Pat. No. 1,590,200 to McGuckin discloses a design that is helpful in addressing the problem of applying high torque forces to a fastening element without slipping across the corners of that element. The drive socket has a tapered cavity to assist in the firm engagement of the fastener element. Furthermore, a substantially longitudinally directed, spiral spline configuration is provided to bite into the surface of the fastener element.
The McGuckin design, however, also presents certain problems. More particularly, the spiral splines only allow a high torque load to be effectively applied in one rotary direction. For example, a spiral spline configuration with a clockwise twist or pitch serves to draw the socket down on the fastening element for secure engagement in the narrower portion of the tapered socket when tightening the fastening element. Conversely, when attempting to loosen the fastening element, such a clockwise spiral spline configuration serves to draw the socket upwardly on the fastening element which is then in registration with the wide portion of the taper. This results in a loss of "grip" that directly leads to slipping and the stripping of the fastening element. Accordingly, the McGuckin drive socket is not adapted to both securely tighten a fastener element and remove an element that is very tightly attached.
Accordingly, a need is identified to provide a drive socket that overcomes the disadvantages of the above-described designs. Such a drive socket would be particularly effective in both securely tightening and removing fastener elements from adhesive-like engagement. The drive socket would be adapted to cooperate with commonly known drive elements such as ratchets or air wrenches.